You know, El Nino, Nina, NAOs -all that sort of thing.
I was going to struggle with this until I found the FAQ below. Editing the post I came across the explanation for a few things both in the post itself and… well just read it yourself… …
Such events are entirely the reult of the lunar phase.
Originally posted by Chris Landsea; AOML:
Lower troposphere westward travelling disturbances seed a large proportion of tropical cyclones over the North Atlantic Ocean. These disturbances, "African easterly waves", had their origins over North Africa. The waves were being generated by an instability of the African easterly jet.
The jet is a result of the reversed temperatures over North Africa, due to heat of the Saharan contrasting with the cooler Gulf of Guinea coast. The waves move generally toward the west across the Atlantic Ocean, first seen in April or May and continue until October or November.
The waves have a period of 3 or 4 days and a wavelength of 1200 to 1500 mi]es. On average, about 60 waves are generated over North Africa each year, but it appears that the number that is formed has no relationship to how much tropical cyclone activity there is over the Atlantic each year.
While only about 60% of the Atlantic tropical storms and minor hurricanes (Cats 1 and 2) originate from easterly waves, nearly 85% of the intense (or major) hurricanes have their origins as easterly waves. It is suggested, though, that nearly all of the tropical cyclones that occur in the Eastern Pacific Ocean can also be traced back to Africa (Avila and Pasch 1995).
It is currently completely unknown how easterly waves change from year to year in both intensity and location and how these might relate to the activity in the Atlantic (and East Pacific).
That last is the first thing I was able to answer. It's pretty obviously the time of the phase. It has to be one of those "on the cusp types" where I have so much difficulty on account of them being difficult types.